This invention relates to an automobile rear windowpane antenna apparatus disposed on a rear windowpane plate of a vehicle and, in particular, to an AM/FM windowpane antenna pattern structure.
The rear windowpane plate is enclosed with a substantially rectangular window edge. That is, the window edge consists of an upper end edge, a lower end edge, a right end edge, and a left end edge. Inasmuch as the right end edge and the left end edge extend in a vertical direction, they are called a pair of rear pillars. In other words, the rear windowpane plate comprises the pair of rear pillars at both ends laterally.
The rear windowpane plate is enclosed with a substantially rectangular window edge. That is, the widow edge consists of an upper end edge, a lower end edge, a right end edge, and a left end edge. Inasmuch as the right end edge and the left end edge extend in a vertical direction, they are called a pair of rear pillars. In other words, the rear windowpane plate comprises the pair of rear pillars at both ends laterally.
The fog preventing apparatus (the defogger) is disposed on the rear windowpane plate at a lower portion thereof. The defogger comprises a plurality of heater lines extending in a horizontal direction and a pair of bus bars which is disposed close proximity to the above-mentioned pair of rear pillars to feed the plurality of heater lines with power. The pair of bus bars extends in the vertical direction. One of the pair of bus bars is connected to a DC power source while another thereof is grounded.
Various automobile rear windowpane antenna apparatuses of the type are already proposed previously. By way of illustration, Japanese Unexamined Patent Application Publication No. H11-261321 (JP-A-11-261321) discloses an automobile rear windowpane antenna apparatus comprising an antenna conductor (an antenna pattern) and a feeding point which are disposed above the defogger at an upper portion of the rear windowpane plate. The antenna conductor is for receiving an AM broadcasting band and an FM broadcasting band. The antenna conductor comprises a substantially horizontal element and a loop-shaped element. The loop-shaped element is disposed between the substantially horizontal element and the defogger. The substantially horizontal element and the loop-shaped element are connected to a feeding point.
In the automobile rear windowpane antenna apparatus disclosed in JP-A-11-261321, the feeding point is disposed between either of the pair of rear pillars and the antenna conductor (the antenna pattern).
Other Japanese Unexamined Patent Application Publications are similar in structure to JP-A-11-261321. For example, in an automobile rear windowpane antenna apparatus disclosed in Japanese Unexamined Patent Application Publication No. 2001-168623 (JP-A-2001-168623), a feeding point is disposed close proximity to a right-upper side portion of a rear windowpane plate when seeing from the inside of the vehicles or the outside of the vehicles. In addition, in an automobile rear windowpane antenna apparatus disclosed in Japanese Unexamined Patent Application Publication No. 2003-168908 (JP-A 2003-168908), a feeding point is also disposed between either of a pair of rear pillars and an antenna conductor (an antenna pattern).
However, if the feeding point is disposed between either of the pair of rear pillars and the antenna conductor (the antenna pattern), the antenna conductor (the antenna pattern) has a smaller effective area. As a result, the conventional automobile rear windowpane antenna apparatuses are disadvantageous in that it is difficult to make a gain thereof large.